Editing IBM Personal Computer (section)

=== Motherboard ===
The PC is built around a single large circuit board called a [[motherboard]] which carries the processor, built-in RAM, expansion slots, keyboard and cassette ports, and the various peripheral integrated circuits that connected and controlled the components of the machine.

The peripheral chips included an [[Intel 8259]] [[Programmable interrupt controller|PIC]], an [[Intel 8237]] [[Direct memory access|DMA]] controller, and an [[Intel 8253]] [[Programmable interval timer|PIT]]. The PIT provides {{nowrap|18.2 Hz}} clock "ticks" and dynamic memory refresh timing.